The tragedy, the worst since the Virginia Tech massacre in 2007,
is one of a spate of deadly mass shootings in America this year.

The violence has spurred discussions about gun laws and mental
healthcare.

Here's a timeline of some of the worst deadly shootings in
the U.S. this year:

January 10, 2012: Three teenagers
were shot dead in an ambush in Philadelphia, CBS reported at the time. The 30-year-old
suspect opened fire on four teens in a car, killing three and
injuring one.

February 21, 2012: Jeong Soo Paek burst
into a spa his family owned in Norcross, near Atlanta, Ga. He
killed four relatives before turning the gun on himself, the
Atlanta Journal-Constitution reported at the time. Police
speculated that financial problems motivated the shooting.

February 27, 2012: A 17-year-old student, T.J.
Lane, confessed to going into his Chardon, Ohio high school
cafeteria and shooting students at random.
Three students died and two were hospitalized, The New York Times reported. Lane said he
stole the gun from a relative who had obtained it legally.

March 30, 2012: A gunman drove by and
opened fire on a crowd of mourners outside a funeral home in
Miami, Fla. Two people died and 12 more were injured, the Miami
Herald reported. The mourners were gathered for the funeral of
21-year-old Marvin Andre, who also died in a shooting.

April 2, 2012: One L. Goh opened fire at
Oikos University in Oakland, California. He killed seven people
and injured at least three more. Goh was a former student at the
school and was said to be angry that he
was expelled for poor behavior, CNN reported.

April 6, 2012: Five African-American men
were gunned down in separate incidents in Tulsa, Oklahoma,
ABC reported. Police arrested Jake
England, 19, and Alvin Watts, 32, and said that the murders were
motivated by racism. Three men died and two were seriously
injured.

May 29, 2012: Ian Stawicki
went to a cafe in Seattle's University district, shooting and
killing four people, ABC reported at the time. He then fled to a
parking lot and shot another woman before killing himself. He
wasn't thought to have known his victims.

July 20, 2012:
James Holmes, 24, allegedly broke into a midnight premiere of
"The Dark Knight Rises" in Aurora, Colo., killing 12 people and
injuring roughly 60 more. Later, police revealed that Holmes, a
doctoral student in neuroscience, spent $20,000 on ammunition and
weapons.

August 5, 2012: Seven people died after gunfire
broke out at a Sikh temple in Oak Creek, Wisconsin. The gunman,
identified by police as
Wade Michael Page, also died in the shooting. He was a white
supremacist and the shootings were said to be racially motivated.

August 13, 2012: Three people including a police
officer were killed in shootings near the campus of Texas A&M
University. The alleged shooter,
Thomas Caffell, was said to be obsessed with video games and
was having financial problems.

August 24, 2012: Jeffrey Johnson
shot a former coworker and injured nine more people before
being shot and killed by police. The shooting occurred near New
York's Empire State Building during rush hour.

August 28, 2012: Robert Gladden Jr., 15,
allegedly
brought a gun to Baltimore's Perry Hall High School and shot
a fellow student, resulting in a critical injury. The boy's mom
said he had been bullied.

August 31, 2012: Ex-Marine Terrell Tyler, 22,
opened fire at the Old Bridge, New Jersey supermarket where
he worked. He killed two of his coworkers before shooting himself
in the head.

September 28, 2012: Andrew Engeldinge
walked into his former office, Accent Signage Systems in
Minneapolis, and
"carefully selected" coworkers to execute. He fatally
shot five people before turning the gun on himself.

October 21, 2012: Radcliffe Haughton, 45,
bought a handgun and drove to a Milwaukee, Wisconsin, spa where
his estranged wife was working. He
killed three people, including his wife, before shooting
himself.

November 6, 2012: Lawrence Jones, 42,
opened fire at Valley Protein, the Fresno, California
meat-processing plant where he worked. He killed two people and
himself. Two more were seriously injured.

December 12, 2012: Jacob Tyler Roberts, 22,
allegedly stole a rifle from a family friend and went into a
Clackamas, Oregon shopping mall with "several fully-loaded
magazines" of ammunition. He killed two bystanders before
shooting himself.

December 14, 2012: A gunman opened fire at a
Sandy Hook Elementary School in Connecticut. At least 27 people
died, including 20 children, according to reports. That story
is still developing.